Produced water and hydraulic fracturing return water that comes up with the oil or gas typically has a complex matrix of dissolved solids and organics in it. These waters are then taken to a disposal well where they are injected into spent wells or into salt caverns. The oil industry requires significant amount of good “quality” water for production, upgrading, and distribution of oil. Historically produced and return waters were not high enough quality to reuse or recycle. This system provides an economical solution for water treatment and therefore can be recycled, reducing the strain on the fresh water supply.
Today, there are several technologies that specialize in the recycling of these waters. They include evaporation, membrane, and oxidation. Evaporation distils the water to create water that is free of dissolved solids, but not hydrocarbons. There are several different membrane systems in use including hollow fibre, ceramic, nano filtration, and reverse osmosis. The first two are designed for solids and some oil removal, and the last two are designed for dissolved solids removal. Membranes have significant issues with heavy metals and hydrocarbons, and therefore require additional technologies to limit maintenance costs. One system currently in the market uses oxygen/uv/tiO2 to create hydroxyl radicals. The system very complex and involves several layers of membranes. Another system uses ozone and sonication, which introduces the ozone into the solution, sonicates the solution to activate the chemical reaction. Both oxidation processes are for hydrocarbon and heavy metal removal.
All of the described processes have challenges, but the common issue is that they are very energy intensive.